Add td::change_user.

GitOrigin-RevId: 8140b771e561d968d6fbf790249364190cb96d6c

tdutils/CMakeLists.txt

@@ -68,6 +68,7 @@ set(TDUTILS_SOURCE
   td/utils/port/StdStreams.cpp
   td/utils/port/thread_local.cpp
   td/utils/port/UdpSocketFd.cpp
+  td/utils/port/user.cpp
   td/utils/port/wstring_convert.cpp
 
   td/utils/port/detail/Epoll.cpp
@@ -146,6 +147,7 @@ set(TDUTILS_SOURCE
   td/utils/port/thread.h
   td/utils/port/thread_local.h
   td/utils/port/UdpSocketFd.h
+  td/utils/port/user.h
   td/utils/port/wstring_convert.h
 
   td/utils/port/detail/Epoll.h

tdutils/td/utils/port/user.cpp

@@ -0,0 +1,55 @@
+//
+// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2020
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+#include "td/utils/port/user.h"
+
+#include "td/utils/port/config.h"
+
+#if TD_PORT_POSIX
+#include <grp.h>
+#include <pwd.h>
+#if TD_DARWIN || TD_FREEBSD || TD_NETBSD
+#include <sys/param.h>
+#endif
+#include <sys/types.h>
+#include <unistd.h>
+#endif
+
+namespace td {
+
+Status change_user(CSlice username, CSlice groupname) {
+#if TD_PORT_POSIX
+  passwd *pw = getpwnam(username.c_str());
+  if (pw == nullptr) {
+    return OS_ERROR(PSTRING() << "Can't find the user '" << username << "' to switch to");
+  }
+  uid_t uid = pw->pw_uid;
+  gid_t gid = pw->pw_gid;
+  if (setgroups(1, &gid) == -1) {
+    return OS_ERROR("Failed to clear supplementary group list");
+  }
+  if (!groupname.empty()) {
+    group *g = getgrnam(groupname.c_str());
+    if (g == nullptr) {
+      return OS_ERROR("Can't find the group to switch to");
+    }
+    gid = g->gr_gid;
+  } else if (initgroups(username.c_str(), gid) == -1) {
+    return OS_ERROR("Failed to load groups of user");
+  }
+  if (setgid(gid) == -1) {
+    return OS_ERROR("failed to set effective group ID");
+  }
+  if (setuid(uid) == -1) {
+    return OS_ERROR("failed to set effective user ID");
+  }
+  return Status::OK();
+#else
+  return Status::Error("Changing effective user is not supported");
+#endif
+}
+
+}  // namespace td

tdutils/td/utils/port/user.h

@@ -0,0 +1,16 @@
+//
+// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2020
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+#pragma once
+
+#include "td/utils/Slice.h"
+#include "td/utils/Status.h"
+
+namespace td {
+
+Status change_user(CSlice username, CSlice groupname = CSlice());
+
+}